In checking water, oil, gas or other pipelines or conduits for leaks, or for other purposes, or for repairing or replacing pipeline sections it was at one time the practice to drain off part of the line, or to sever the pipe and cap the exposed end thereof with a plate or similar cover. This, of course, was a time consuming and expensive procedure.
More recently the accepted method has been to freeze a section of the pipe, a water pipe, for instance, without cutting it or draining it of its contents; and thereafter testing or repairing, or working on that portion of the pipeline which is located "downstream" of the frozen pipe section. After the testing, repairs, or pipe work or replacement has been completed, the section that was frozen and its contents are permitted to thaw, thus resuming the flow of water through the pipeline as a whole.
A most widely used technique to freeze a section of the pipe is to spray refrigerant gas directly onto the pipe section. This is extremely expensive.
According to another practice in the trade a ring like or annular cover is placed around a small section of pipe and provided with radial lips that seal the end portions upon which the pipe section to be frozen rests. The arrangement is such that there is a free space or clearance between the outer periphery of the pipe's surface and the inside surface or inner face of the annular member surrounding the pipe section. A refrigerant cooled by a conventional refrigerating unit is circulated through the clearance between the pipe and the annular member, the refrigerant being in actual contact with the outer surface of the pipe section as well as with the inner surface or face of the annular ring like component. With this arrangement, water inside the pipeline section is frozen so as to form therein an "ice plug", thereby blocking passage of the water through the pipe and permitting repairs to be made, or testing procedures, or replacements, or whatever else may be necessary or desirable, "downstream" of the ice plug without cutting or severing the pipe or draining its contents.
The practice just referred to wherein the refrigerant is charged into a gap or clearance between the pipe work piece and the ring like or annular member that encloses the pipe is not without its disadvantages. For one, the preferred refrigerant, namely, brine, is, of course, a strongly saline solution of sodium chloride or calcium chloride either of which is difficult and expensive to use. Other refrigerant materials as, for example, sulpher, dioxide or methyl bromide are more efficient from the point of view of cost but are also much more hazardous to use. As will be understood they can produce seriously adverse effects, and even death.
Another disadvantage of the prior systems is cost. Some of these are operated or controlled by hand valves or the like; or require cumbersome and expensive latching devices to maintain an air tight seal against refrigerant leakage in or from the passageway between the pipe to be frozen and the ring like annular member embracing it in spaced relationship therewith.
The present invention contemplates a method and means for eliminating or reducing at least some of the prior art disadvantages specified. To these and other ends it proposes a self contained refrigeration system with freezer unit within which the refrigerant is circulated and recirculated, out of contact with the pipe section and its contents which are to be frozen.